Andrei Alisenok

el.addEventListener('click', ()=> {
if (el.checked) {
...
}
})

<input type="text" class="question">          
<input type="text" class="answer">

let question = document.querySelector('.question')
let answer = document.querySelector('.answer')

question.addEventListener('input', (e) => {
    e.preventDefault()
    answer.value = question.value
})